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The National Police Air Service supported the investigation, and it was said that the attackers left the area "in a number of directions".

Detective Inspector Anna Martin said: "The attackers left the area in a number of directions, some onto Couchmoore Avenue, going towards Hinchley Wood while we believe others may have gone onto the railway track.

"I would urge anyone who saw what took place near to the bridge or anyone who has any information about it, possibly through comments, pictures or videos, that they’re aware of via social media channels, to get in touch with us urgently."